Wireless communications networks, such as wireless LANs, can allow network-enabled stations (STAs) to access a network, via an access point (AP) by communicating wirelessly. The access point (AP) is typically also considered an STA.
Standard-setting organizations provide standards by which devices from various manufacturers can communicate with one another.
The IEEE 802.11 standard governs wireless connectivity in local area networks. IEEE 802.11 specifies a basic service set (BSS) 10 as consisting of a single AP 12 with one or more associated STAs (A-STA) 14, 14′, as illustrated in FIG. 1. An example STA 20 is schematized in FIG. 2 and can be seen to have one or more processor(s) 22, memory 24, and one or more radio(s) 26, with each radio 26 typically having a transmitter 28, a receiver 30, and one or more antenna(e).
Accordingly, each STA 14, 14′ can have a uniquely addressable medium access control (MAC) and a physical layer (PHY) interface to the wireless medium (WM). IEEE includes specification that functions to associate an enabled STA 14 and the AP 12 thereby causing the enabled STA 14 to become an associated STA (A-STA). During this process, IEEE 802.11 defines a receiver address (RA) and a transmitter address (TA) for the MAC frame header. IEEE also includes specifications for dealing with BSS's having overlapping ranges (which can be referred to as OBSS—not illustrated).
More specifically, amendment IEEE 802.11ad-2012, referred to as IEEE 802.11ad, addresses the use of wireless in the 60 GHz “millimeter” wave band, a band which is unlicensed globally, thus making it available for use in local area networks (LANs). In particular, communication in the 60 GHz band, although directional and strongly attenuated (short range), is perceived as having a strong potential for replacing cabled connections (e.g. Ethernet) and providing multi-gigabit transmission speeds.
Under IEEE 802.11ad, wireless communications between stations have a format which can be referred to as the beacon interval (BI) 40. FIG. 3 schematizes the BI 40. The BI 40 can be seen to generally include a beacon transmission interval (BTI) 42, an associating beamforming training (A-BFT) 44, and a data transmission interval (DTI) 46. The BTI 42 is used for AP discovery purposes and, more specifically, for AP-side sector sweep transmit antenna beamforming training purposes. The A-BFT 44 can be used mainly for STA-side sector sweep transmit antenna beamforming training purposes. The DTI 46 can be used for further beamforming training and for data communication. The BI 40 can further include additional intervals, such as an announcement transmission interval (ATI) (not shown), which can immediately precede the DTI 46, for instance.
Under IEEE 802.11ad, STA's 14, 14′ can be referred to as directional multi-gigabit (DMG) STA's, and the beacon can be referred to as the DMG beacon. Under IEEE 802.11ad, APs 12 are sometimes referred to as personal BSS (PBSS) control points, (PCPs). Both expressions will be used interchangeably in this specification.
DMG communications typically involve STA's having a plurality of antenna sectors. The different antenna sectors offer different performance in different directions. IEEE 802.11ad includes beamforming (BF) specifications which refer to a process by which the directional link is ‘trained’ to meet the required link budget. These specifications include a sector level sweep (SLS) process 50 such as shown in FIG. 4. The station initiating the SLS 50 is referred to as the initiator, and the other station is referred to as the responder. During SLS 50, different combinations of initiator antenna sectors and responder antenna sectors are tested to find a satisfactory combination. More specifically, in a first phase of the SLS, sector sweep (SSVV) frames 52, (sometimes alternatively referred to as BF frames) are emitted sequentially by the different sectors of the initiator antenna. The first phase of SLS can be conducted during a beacon transmission interval (BTI) 42 portion of the BI 40, for instance.
In a second phase of the SLS 50, the responder transmits SSW frames 54 sequentially through its different antenna sectors. The SSW frames 54 emitted by the responder include feedback pertaining to the strength of the signals received from the different sectors of the initiator. The second phase of the SLS 50 can be performed during an A-BFT 44 or DTI 46 of the BI 40, for instance.
In a third phase, the initiator can transmit SSW feedback (SSW-FB) 56 to the responder. The SSW-FB indicates the strength of the signals received from the responder's different antenna sectors and the selected sector and antenna.
In a fourth phase, the responder can send an acknowledgement of the SSW-FB 58. The SLS process 50 can determine combination of sectors functional to enable efficient directional communication.
The SLS process 50 is typically followed by a beam refinement procedure (BRP) which can search to find optimal parameters for a given sector combination. Beam tracking can be performed to check and attempt to correct signal quality during data transfer. The standard SSW frame 60 defined at 8.3.1.16 of 802.11ad is depicted in FIG. 5 and has 26 Bytes.
Since the SSW frame 60 is repeatedly used by both initiator and responder during SLS 50, the side of the field (i.e. the number of bits) is directly related to bandwidth usage. It is therefore desirable that the SSW frame format 60 be limited in size while maintaining its functionality and, to a certain extent, account for eventual evolution of the standard. In the case of IEEE 802.11ad, when the AP 12 is the initiator and an associated STA 14 is the responder, several fields of the SSW frame 60 were left unused. There thus remained room for improvement.
Document IEEE 802.11-16/0416-01-00, entitled Short SSW Format for 11ay, was submitted Mar. 14, 2016. This submission occurred in the context of the 11ay amendment which aimed to build upon 11ad. This document proposes providing a short SSW frame 65 capability which can be used instead of the 11ad standard SSW frame 60 when both stations are determined to support it. Under 11ay, STAs 12, 14, 14′ having a radio transmitter capable of transmitting and receiving enhanced DMG (EDMG) physical layer (PHY) protocol data units (PPDUs) are provided. Accordingly, this short SSW frame capability may require that both STAs undergoing the SLS be EDMG STA's. The short SSW format 65 proposed in this document is presented in FIG. 6 and has 6 Bytes. The proposed short SSW frame format 65 can be described as the standard SSW frame format 60 with several fields compressed or removed.
Indeed, the non-short SSW frame format 60 includes the receiver address 62 (48 bits), and the transmitter address 64 (48 bits). The proposed short SSW frame format 65 includes a 16 bit addressing field 66 to replace the 96 bits of the non-short SSW frame format 60. It will be noted that this proposal does not define the addressing field format 66 for the short SSW format.
While existing protocol and submissions concerning the 60 GHz wave band were satisfactory to a certain degree, there remains room for improvement.